The Transportation Security Administration has bad news for tens of millions of Thanksgiving holiday travelers: Lines at airports may be even longer than usual as the agency tries once again to plug security holes in its baggage screening.

TSA is scrambling to respond to yet another damning investigation of its screening effectiveness, for the second time in little more than two years. And the agency is already phasing in revised security procedures — including those for passengers’ electronic devices — that could cause “a slight increase in wait times,” new TSA Administrator David Pekoske said in an interview.

“The procedure is new,” Pekoske said. “It’s new to passengers. It’s somewhat new to our screeners.”

The additional delays may not be as horrendous as the hourslong queues that left many passengers stranded at airports in the summer of 2016, a year after TSA leaders launched a crash course in security improvements in response to a previous failing grade from its inspector general.

But Pekoske said travelers could experience some of the longest wait times of the year on Sunday when many return home from the holiday. TSA has projected that more than 2.6 million passengers and airline crew members will be screened on Sunday alone, potentially making it one of the agency’s top five busiest days ever.